This undated image released by PBS shows an endangered Diademed sifaka (Propithecus diadema) at Lemuria Land in Madagascar. National Geographic photographer Joel Sartore is documenting thousands of rare animal species. His quest is detailed in the PBS series “Rare: Creatures of the Photo Ark”, a three-part series debuting Tuesday at 9 p.m. EDT. (Photo by Joel Sartore/PBS via AP Photo)

A squirrel monkey rests on a tree branch on a hot day at a zoo in Zhengzhou, China on July 20, 2017. (Photo by Reuters/China Stringer Network)

Flamingos stand in their enclosure at the zoo “Hellabrunn” in Munich, Germany, Monday, July 17, 2017. (Photo by Matthias Schrader/AP Photo)

A great white pelican looks on in his enclosure at the zoo “Hellabrunn” in Munich, Germany, Monday, July 17, 2017. (Photo by Matthias Schrader/AP Photo)

A newly hatched Loggerhead turtle (Caretta Caretta) makes its way to the Mediterranean Sea at Davultepe District's beach in Mersin, Turkey on July 19, 2017. Caretta Carettas are under protection due to high risk of their extinction. (Photo by Mustafa Gungor/Anadolu Agency/Getty Images)

These Eurasian Otters seem ready for any danger as they all stand up on thier hind legs alert to any threats near to the English river bank. Amateur photographer and retired MOD worker Tony Moir, 57, spotted the otters whilst looking for kingfishers to photograph near the river Trent in East Yorkshire, UK. He was able to take just a couple of pictures before the excited animals spotted the photographer and ran away. (Photo by Tony Moir/Solent News)

A jaguar (Panthera onca) hunts a fish as it swims in its enclosure at Pessac Zoo on the outskirts of Bordeaux on July 20, 2017. Two jaguars – “Catalina” and “Mato” two and one years old respectively – are on display at the zoo on the outskirts of Bordeaux for the first time in Europe and have an enclosure which includes a pool of some 100 cubic metres where members of the public can observe their predatory aquatic abilities. (Photo by Mehdi Fedouach/AFP Photo)

A Bulldog rests after competing in the annual dog fashion show in the Brooklyn borough of New York City, U.S., July 15, 2017. (Photo by Stephanie Keith/Reuters)

A two-month-old unnamed male baby elephant chases a bird at the Africam Safari Zoo in Puebla, Mexico on July 19, 2017. (Photo by Edgard Garrido/Reuters)

A two-month-old unnamed male baby elephant walks with another elephant at the African Safari Zoo in Puebla, Mexico on July 19, 2017. (Photo by Edgard Garrido/Reuters)

Weaver birds build a nest on a bamboo tree in Lalitpur, Nepal on July 21, 2017. (Photo by Navesh Chitrakar/Reuters)

An Atlantic Puffin holds a mouthful of sand eels on the island of Skomer, off the coast of Pembrokeshire, Wales July 18, 2017. (Photo by Rebecca Naden/Reuters)

A swan is released back onto the river during the annual Swan Upping census on July 17, 2017 on the River Thames, South West London. The historic Swan Upping ceremony dates back to the 12th century, to when the Crown claimed ownership of all Mute Swans and they were eaten at banquets and feasts. The Sovereign's Swan Marker, David Barber, counts the number of young cygnets on the river each year and ensures that the swan population is maintained. The swans and young cygnets are also assessed for any signs of injury or disease. (Photo by Leon Neal/Getty Images)

In this photograph taken late July 19, 2017, a poodle wearing small booties stands near its owner at a sidewalk in downtown Hanoi. (Photo by Roberto Schmidt/AFP Photo)